Gas turbine auxiliary power plant



Aug 11, 1953 H. J. woon GAS TURBINE AUXILIARY POWER LANT Filed Aug. 6. 1948 6 Sheets-Sheet l Aug. l1, 1953 H. J. wooo 2,648,491

GAS TURBINE AUXILIARY POWER PLANT Filed Aug. 6, 1948 6 Sheets-Sheet 2 neocon ZYQWYWQ Aug. l1, 1953 H. J. woo

GAS TURBINE AUXILIARY POWER PLANT v 6 Sheets-Sheet 3 Filed Aug. 6, 1948 M ,.wm e0@ O 0 M www@ ad; V Aw Nuf /f NrC Aug. 11, 1953 H. J. WOOD. 2,648,491

GAS TURBINE AUXILARY PQWER PLANT Filed Aug. 6L 1948 es sheets-smet 4 Aug 1l, 1953 H. J. WOOD 2,648,491

GAS TURBINE AUXILIARY POWER PLANT I I Filed Aug. 6, 1948 6 Sheets-Sheet 5 Aug. 11, 1953 H. J. woon 2,648,491

r GAS TURBINE AUXILIARY POWER PLANT Filed Aug. 6. 1948 Patented Aug. 11, 1953 GAS TURBINE AUXILIARY POWER PLANT Homer J. Wood, Sherman Oaks, Calif., assgnor to The Garrett Corporation, Los Angeles, Calif., a corporation of California Application August 6, 1948, Serial No. 42,984

1 Claim.

rIhis invention relates generally to power plants and, more particularly, to a hot gas turbine compressor unit especially adapted as a source of auxiliary power aboard an aircraft.

It is highly desirable in aircraft of the larger types that an auxiliary power means be provided for starting the engines, for operating electrical generators, cabin supercharging equipment and other accessories so that the full power developed by the aircraft engines can be utilized for propelling the airplane. Itis also important that such an auxiliary power unit be very compact so that it occupies a minimum space, and light in weight so that the weight of the aircraft is not materially increased or its pay-load decreased to any appreciable degree.

It is an important object of this'invention to f provide a power unit which meets the abovenoted requirements and which is highly eicient in operation, delivering maximum power per unit of weight.

Another object of the invention is to provide a power unit of the hot gas turbine compressor type which is adapted to supply power either through a mechanical 4drive or in the nature of compressed air for directly or indirectly operating various mechanisms and controls, such as those employed in aircraft.

Another object is to provide a turbo-compressor in which the compressor may supply air to the airplane pneumatic system as well as to the hot gas turbine, the air supplied to the combustion chambers for the turbine being divided at the entrances or inlet ports of the combustion chambers. In accordance with the invention, at least one combustion chamber is provided, in which fuel is burned to heat the power air, this air then being expanded through the hot gas turbine.

Another object is to provide a turbo-compressor power unit which includes a hot gas turbine, a compressor and an accessory case for controlling the operation of the unit, these components being arranged in a line in the order named and each being a separate entity capable of being disassembled from the power unit for repair, inspection and testing. The combustion chambers are disposed at opposite sides of the assembly referred to above and adapted for convenient detachment from the power unit assembly without disturbing the other components and this is another object of the invention.

Another object is to provide a power unit, of the class referred to, in which the individual components are designed such that the unit as a Whole is small, compact and light in weight and thus particularly adapted for use in aircraft.

Another object is to provide a turbo-compressor power unit in which slender torsion bars or shafts are employed for transmitting power from the turbine to the compressor so that slight misalignment between major components can occur without presenting mechanical difficulties. By this means, exact alignment of the components is unnecessary and precision fitting ofthe various housings composing the unit is avoided.

Another object is to provide a power unit of the type indicated in which a two-stage compressor having backwardly curved impeller vanes and a double-volute discharge opening is employed. By this construction, wide variation in air flow rate, without pulsation hazard or serious efficiency loss is effected, the two stages being required to provide sufcient air pressure due to the backward curved impeller vanes, and the double-volute dischargeproducing better aerodynamic balance, heater unit configuration and simplied scroll geometry.

Another object is to provide a turbo-compressor power unit in which the hot gas turbine is of the radial inward-flow reaction type having radial blades. A turbine of this type is much simpler to manufacture than axial-now turbines of comparable size and is capable of obtaining high eiiicienc-ies over a wide range of operating conditions. Moreover, the structural strength of such a turbine wheelis superior to one of comparable cantilever blade `radial-flow type and to one of the axial-flow type. I

Another object is to provide a power unit of the class designated in which the compressor impellers are fully shrouded so as to` effectively reduce end thrust loads and obtain higher eniciencies.

Another object is to provide a power unit of the class referred to in which the turbine wheel and its shaft are machined from a single forging of refractory alloy, in-which an air seal is provided at the rear of the Wheel to balance axial thrust and inner portion of the wheel is exposed to ambient air for cooling purposes. Another object in this respect is to provide a turbine wheel of the radial inward-flow type, similar to a, radial blade centrifugal compressor impeller, such a wheel lending itself to easier fabrication Ythan conventional axial-now wheels and having lower stresses than other wheels of radial-iiow types.

.A further object isto provide, in a turbine of the aforementioned type, means for sealing the turbine wheel to prevent loss of the pressurized gas from the turbine which would decrease the efficiency of the power unit in which the turbine is incorporated.

A still further and important object is to provide a hot gas turbine wherein the thrust on the wheel by the hot gas exhaust is balanced by an equal thrust on the outer peripheral back side of the wheel, which thrust is provided bythe pressure of the hot gas at Athe exit from the nozzles, the remainder of the back side of the tur" bine wheel being cooled by ambient air.

Further objects of the inventionfwill appear from the following detailed description and from the drawings, which are intended'for the purpose of illustration only, and in which:

Figure l is a perspective view compressor power unit; l

Fig. 2 is a side elevational view of the power unit, a combustion chamber being shown in section, taken on the line 2-2 of Fig. 1;

Fig. 3 is an end view as viewed in the direction of the arrow 3 in Fig. l;

Fig. 4 is a longitudinal Vertical sectional View, taken on line lad of Fig. l;

Fig. 5 is an enlarged sectional view of a portion of the hot `gas turbine, showing the sealing means;

Fig. 6 is a schematic planview of the power unit, indicating the Iair flow pattern; and

Fig. 7 is a longitudinal sectional view through the rearward end of a turbo-compressor power plant, showing a modified type of power take-off means in the form of a mechanical transmission by which an electrical generator is driven.

Referring to Figs. 1 to 6 of the drawings in detail, the present improved power plant shown therein is of the hot gas turbine compressor type and includes a hot gas turbine, indicated generally by the reference character iii, a twostage compressor II and a pair of combustion chambers I2 and I3. The turbine i3 and conpressor II are-disposed in axial alignment and each comprises a separate component or assembly adapted to be readily interchanged.

The hot gas turbine Ii! includes a nozzle ring I5 which has a stator shroud I6 secured thereto, the shroud being curved inwardly and terminating in a tubular forward end il, the inner side of which provides the exhaust tube of the turbine.- An enclosure I8 surrounds and is affixed to the tube I'I and has its yforward ared end I9 projecting beyond the end of the tube to lprovide an axial extension thereof. The enclosure I8 extends radially outward frointhe tube il and then rearwardly to be secured to the nozzle ani nulus I5. An yannular hot gas inlet passage is thus provided between the shroud I6 and the enclosure I8 into which hot gas is introduced by way of curved tubes 22 and 23 leading from the combustion chambers I2 and i3, respectively. The nozzle annulus I5 is provided with a series of inclined vanes 24 around its periphery, the spaces 25 between the vanes constituting nozzles through which the hot gas is directed against the blades 29 of a turbine wheel 30, to be later described. The nozzle annulus i5 is substantially channel shaped in cross section so as to provide an annular air space 26 in its rearward face, as best shown in Figs. 4 and 5.

Secured to a flange of the'nozzle annulus I5 by means of bolts 30 is the peripheral portion SI of a bearing housing 32 which has an axial sleeve-like portion 33. Within the sleeve portion 33|, at the ends thereof, are anti-friction bearings 34 which rotatably support the shaft of the turbine 35 of the turbine wheel 36, it being noted that the shaft 35 is formed integral with the wheel so as to obtain maximum strength and close balance. It will also be observed that the turbine wheel is of somewhat unconventional design, in that it is of a radially inward-flow reaction type and resembles an impeller of the radial blade type such as commonly employed in centrifugal compressors where the air is forced radially outward by the blades.

Secured to the annular portion 3I of the bearing housing 32, by screws 37, is an annular carrier member 33. By this provision, ambient air can contact the back of the turbine wheel 33 for the purpose of cooling the same, the air entering the housing 32 through apertures 40 in the side thereof. In its face which is disposed adjacent the wheel 33, the carrier member 33 has a pair of concentric annular grooves 42 for receiving annular sealing rings 43 which are held in place by snaprings Q5. The sealing rings 43, which are preferably made from stainless steel, are angular in cross section and have resilient portions 4t which engage against the outer inclined surfaces of V-shaped annular lands il formed on the back of turbine wheel 33. By this means, leakage of the hot gas from the rearward side of the turbine is prevented. The hot gasentering the turbine unit. I3 from the combustion chambers I2 and I3 is received in an annular space 48 defined by the inner surface of the nozzle annulus I5, the back of the turbine wheel 3U, the outer sealing ring 43, the carrier member 38 and a ring 49 secured between the member and annulus i5. This gas exerts a pressure against the outer peripheral portion of the back of the turbine wheel 3i] and thus counteracts the rearward axial thrust of the turbine wheel and this is an important feature of the invention. Itis thus seen that except for its outermost peripheral portion, the back of the turbine wheel 3E) is exposed to ambient air and is cooled thereby. The bearings 3ft for the turbine wheel shaft 35 are supplied with lubricant forced through a tube 5I] connected to a suitable pump (not shown). A sealing device 5I is employed for preventing loss of the lubricant from the forward end of the sleeve portion 33. Fast within an axial bore at the inner end of the turbine shaft 35 is a sleeve 52 having a splined inner surface.

It will be observed from the foregoing the turbine i@ is a self-contained unit capable of being made as a sub-assembly cf the complete auxiliary power plant. It will alec be apparent that the turbine unit itl is particularly well adapted for convenient aesernblf disassembly so that inspection of its internal parts and replacement thereof is greatly facilitated. To further facilitate the assembly and disassembly of the parts, the housing 32 and the carrier member 33 are connected by bolts 53 so that by removing the bolts 33', the bearing assembly, including the hor-sing ai carrier member can be detached from the nozzle annulus i5.

rlhe hot gas turbine, which is of the radial inward-flow reaction type having radial blading has beeny found highly advantageous for severalreasons. In the first place, fabrication of the turbine wheel. is much simpler than for an axial-flow type wheelof comparable size. Moreover, structural strength of the present turbine wheel is superior to comparable wheels of the cantilever-blade radia-flow types. Furthermore, it has been determined that high efciencies over a wide range of operating conditions are derived through the use of the instant turbine unit.

The compressor unit II, which is also made as a subassembly of the power plant, is of the two-stage type. The unit II includes a compressor housing 55 which has a forward funnelshaped end 55 provided with a peripheral ange 55 which is adapted to abut the side of a similar flange l oi the turbine bearing housing 32 and to be secured thereagainst by bolts 58. The end 55 of the compressor housing 55 has an axial b-ore in which bearing bushings 59 are held, these bushings providing bearings in which the forward end of a tubular compressor shaft S3 is adapted to rotate. Lubricant is supplied to these relatively rotating parts through passages 54 and lines 65 connected to the oil pump previously referred to. The compressor shaft 63 has a bore 67 which is reduced in diameter as indicated at E8, this reduced portion havingl splines on its interior. A quill shait lll, which extends coaxially through the shaft has splined ends which engage in the splined portions 58 and 52 of the shaft and the sleeve 52, respectively. It is thus seen thatV when the turbine wheel is driven, torque is imparted through the quill shaft 'lil to rotate the shaft 53 and the compressor impellers carried thereby. The quill shaft lo is adapted to flex and to twist somewhat so that it provides a substantially resilient driving connection between the turbine and the compressor units. Due to the flexibility of the quill shaft substantially vibrationless performance is achieved, Moreover, the quill shaft makes for ease of assembly of he components of the power unit since it compensates for slight axial misalignment of the components.

The compressor housing 55 is provided with an enlarged generally cylindrical rearward portion i2 having a peripheral flange 'i3 at its rearward open end and an air inlet opening 'I4 in its forward wall. The opening le is in communication with an air inlet connection Ma intersecting a plane normal to the power plant axis which passes through both combustion chambers. It is to be noted that this inlet connec tion is spaced substantially upwardly from a plane extending through the upper surfaces of both of the combustion chambers, so that air may be supplied to the compressor unit without substantial heating by the combustion chambers, and thus enable bleed air for pneumatic power purposes to be obtained from the compressor, as 'will hereinafter be explained. A pair of annular chambers 79 and 80 are formed within the rear portion l2 of the housing 55, these chambers being dened by the wall of the hous ing, an annular plate l5, an annular wall structure '55a and shrouds 'i5 and ll. A iirst stage compressor wheel or impeller BI is fast on the shaft 63 adjacent the bearing 59 and has rearwardly curved radial vanes 82 the inner forward portions of which register with the air inlet opening 74. Thus, during rotation of the compressor wheel 8i air drawn into the housing l2 is forced radially outward then radially inward and is compressed within the wheel and within the diiuser vane section 79a (Fig. 4). rThe air is then further compressed in a second stage compressor by the impeller 53 having similarly rearwardly curved radial vanes 54 and by the diiTuser vane section 80a (Fig. 4), the air being directed radially outward into the second chamberSc which, as will be Vshown hereinafter, com- 6 municates with the combustion chambers I2 and I3.

Secured to the peripheral iiange 'I3 of the compressor housing 55, 12 by bolts 8l is an annular member 88 which has walls defining a pair oi volute discharge passages 89 and 55 which communicate with the circular compression chamber 50 through openings SI. The walls of the passages 89 and 90 provide volute discharge ducts S2 and 93 which, as shown in Figs. 1 and 3, extend laterally outward from the compressor unit II. As shown in Fig. 4, the member 88 has a central portion S5 which Vis provided with an axial bore in which suitable anti-friction bearing means, indicated at 9E, is disposed. The bearing means 96 rotatably supports the rearward end of the tubular compressor shaft 63 and takes the axial thrust of the shaft. The bearing 96 is preferably lubricated by a pressure system (not shown).

The centrifugal compressor I l, which is of the two-stage type employing impellers provided with backward curved impeller vanes and having a double-volute discharge, has been found to be particularly suitable for use in the auxiliary power plant. rl'he backward curved vanes permit wide variation in air flow rate without pulsation hazard or serious efficiency loss. The double-volute discharge provides greater aerodynamic balance, more desirable unit design and simplied scroll geometry. As will be noted from the foregoing description, the compressor unit I I is designed as a separate unit and can be detached from the turbine unit I Il by merely removing the bolts 58, the forward end of the quill shaft it sliding out from the splined sleeve 52 to permit such disassembly. It will also be apparent that by disconnecting the scroll member 83 from the compressor housing portion 12, the shafts 63 and l0, together with the impellers 8i and 83, can be readily removed from the housing as a unit for inspection or reconditioning purposes.

In order to minimize radial bearing loads, the impellers are balanced as separate components prior to balancing of the complete assembly so as to prevent serious shaft deiiections at high speed, it being pointed out that in the present power plant the impellers 8l and 83 are rotated at a maximum speed of approximately 40,000 R. P. M. The compressor impellers are fully shrouded, as shown in Fig. 4, so as to reduce end thrust loads and obtain higher efficiencies. The rst stage impeller 8l has a short diffuser around its periphery and only a portion of the velocity reduction occurs at this point. The air passages which duct the air to the second stage inlet also function as diffusers, full diffusion being'accomplished in the second stage diffuser.

Connected to the ends of the volute discharge ducts 92 and 93 by means of exible duct couplings 99 andIIl and a bolt Ill (Figs. 2 and 3) are elbow shaped air ducts II and 02, respectively. The ducts 10i and I02 have portions 53 and |04, which provide extensions of the ducts 92 and 03, and forwardly extending portionsl or shells and E95 which are arranged substantially parallel to the axis of the power unit and which constitute the outer housings or shells of the respective combustion chambers I2 and I3 (Fig. 2). The portions ID3 and Ifl of the elbow shaped ducts II and I 02 are extended laterally in air discharge tubes or branches lill and les having flanged ends by which suitable ducts (not shown) canbelconnected. Q. The rtubea island rotate the latter at a high rate of speed. 4ring to Fig. 6 ofthe drawings, the direction of |08 constitute bleed-offsthrough which air compressed within the compressor unit il can flow to the airplane pneumatic power system. AWithin theelbow ducts lill and |02 are angular vanes H (Figs. l and 2) which serve to divide the compressed air so as to divert the proper amounts into the shells S65 and it. Disposed concentrically within they shells H35` and iii are perforated tubes H2 which form extensions of the hot gas inlet tubes 22v and 23 of theturbine unit lil. The rearward end of each tube l2 is tapered and is connected to a sleeve i3 in which a fuel nozzle H5 is disposed, fuel being supplied to the nozzle through a tube ii@ which is connected to a suitable fuel pump to be later identified in the drawings. rhe forward end of each shell it and i' is connected to an enlarged portion lil of the tube l I2 by means of a clamping ring l i8. Azglow plug H9 (Fig. l) extends through the side of each shell |05 and liliiand tube H2 and is connected in an electrical circuit, energization of the plug serving to ignite the fuel to effect combustion of thel latter. The compressed air entering the tubes i l2 is thus heated within the combustion chambers i2 and i3 and enters the turbine unit through the curved inlet tubes 22 and 23 and is directed against the blades '9 of the turbine wheel 3d and expanded therein to Referflow of the air is indicated by the arrows.

The ambient air, upon entering the inlet opening i4 of the compressor unit i l, is compressed by the two stage compressor and forced laterally ythrough the volute discharge ducts lill and |932 Yand into the combustionvchambersiii: and ,i3

where the enthalpy of the compressed air is increased by the combustion of fuel therein, this being accomplished with as near an approach as is possible to a constantpressure desideratum. rfhis higher` energy level air is then directed by the curved inlet ducts 22 and 23 and the enclosure i8 through the nozzles to rotate the turbine wheel 36, the air then exhausting through the discharge Vtube lil. The iiow of the air through the cycle referred to above is indicated by full line arrows in Fig. 6. During the operation of the auxiliary power plant, a vportion of the compressed air is diverted through the branch tubes lill and |08, as indicated by the dotted arrows, to the airplane pneumatic power system or to other pneumatically operated mechanisms. It. is to be noted that each combustion chamber, including the shell i or iil, the connected ducts itl and |92 respectively, together with the fuel nozzle. H5 can be readily disassembled from the power Aunit by merely disconnecting the clamping ring dit .and the bolt iili.

Attached to the rearward end of the scroll member 88 by bolts i25 is a frame |2| (Figs, 2, 3 and 1l). Detachably connected to the frame l2| is an accessory unit, indicated generally by the reference character |22. The accessory unit E22 includes a support member or casing |23 which is secured to the frame I2! by bolts liil and on which the several-accessories are mounted. Cnc

vof these accessories is an electrically operated starter |25 which has a tubular shaft extension H26 rotatable in a 'bearing boss lill of the sup- 1port member l23;

; than the star-terspeed orvwhen thestarter is der energized. In eitherreventthestarter remains`v all) de-clutcheduntil such time as both starter and turbine come to rest. The shaft extension |26 has aspl-inedbore for receiving the rearward splined end of a relatively short, flexible starter shaft |28, yThe forward end of the shaft |28 is similarly splined vand received in the splined portion 38 of the tubular compressor shaft 63. It is thus seen that when the starter |25 is energized, torque is transmitted through the shaft |28, to the compressor shaft S3 to rotate the compresser impellers 8| and 83so as to initially start the powerl unit. After the turbinewheel 3S has started to rotate in response to the passage of hot gas therethrough and the` compressor impellers 8| and 83 are driven from theturbine unit, the starter motor is deenergized.

A fuel control device |38, preferably 0f lthe governor type, isalso mounted on the support member |23 and has a gear |3| which is driven from a gear |32 onthe tubular shaft extension 126.; Also mounted on the support -member |23 below the fuel controldevice |3 is a fuel pump |33 having a shaftv |34 and a -gear |35 on the shaft which meshes with a smaller gear |3 rotatable with the gear |3|. An oil pump Mil is attached to the support member |23 below the fuel pump |33 (Fig. 3) and driven from the gear |35. t is thus seen that the several accessories are driven continuously by and during the rotation of the shafts |28 and 63. Since the accessories mentioned above `may be of any suitable types, they are not herein shown or described in detail. The pressure lubricant system, which includes the oil pump .m0, also includes an oil tank or reservoir'MZ -(Fig. 2) which is connected by a line M3 to the inlet port of the pump, and a by-pass line |44 leads from the by-pass port of the pump back to the reservoir. An oil pressure line m5 connected to the pump |40 supplies oil to the several bearings of the power unit, the oil then returning to the reservoir |42 .through a line |46 to be recirculated.

Since the power absorbed by the compressor is a function of air flow rate, the amount of fuel burned in the combustion chambers is determined 'by air flow rate. Control is acomplished by maintaining substantially constant turbine speed through the agency of the governor. Thus, an increase in supply air flow tends to absorb more power, the power unit tends to reduce in speed and the governor increases the fuel supplied in order to compensate for this reduction in speed. 4 It will be observed from .the foregoing that the present invention provides a hot gas turbine compressor power kunit which is particularly adapted for supplying compressed air for use in various pneumatically operated controls and mechanisms. However, it is within the concept y of this invention to provide a direct mechanical assembly. Similarly, the compressor and accessory case are made as separate units adapted to be connected to and disassembledfrom the power unit.. The combustion chambers are likewise readily. disassembledwithout disturbing the other 91 components of the power unit, The power plant is particularly adapted for use as an auxiliary power supply aboard an aircraft since it is extremely compact, light in weight and highly efcient in operation.

The invention has thus far been described as embodied in a turbo-compressor unit in which a portion of the air compressed by the compressor unit is discharged from the unit and utilized as a source of pneumatic power for operating various aircraftl controls or air-driven mechanism. It is within the concept of the invention, however, to provide a turbo-compressor power unit in which the compressor shaft is utilized as the source of direct power for operating an aircraft generator or other equipment. Such a modified version of the power unit is disclosed in Fig. '7 and constructed in the manner next described.

In the alternative structure illustrated in Fig. 1, the turbine unit and the air compressor unit may be of substantially the same construction as previously described in connection with the embodiment shown in Figs. 1 to 6 and therefore are not shown in detail. In this alternative embodiment, in some cases the compressed air is not bled off for the purpose of providing pneumatic power and for this reason the air ducts |G| and |92 have no branch lines lli and l 08 but rather these ducts merely have curved elbows. Because of this fact, it will be apparent that a compressor unit of smaller capacity or a turbine unit of larger size may be desirable.

In Fig. '7, the reference character Sii designates the rear portion of the compressor housing and 5| represents the scroll member or discharge member which is bolted to the end of the compressor housing and which is substantially the same as the member 88 described in connection with the embodiment illustrated. in Figs. l to 6. The rearward end of the tubular compressor shaft |52 is rotatable in an anti-friction bearing |53, disposed axially within the air discharge member 5 and has an internally splined portion |54.

Secured to the rearward end of the air discharge member |5|, by bolts |55, is an annular transmission housing |51 which has a rear end plate |58 provided with a hub |59 having a bore in which anti-friction bearings |66 are retained by suitable means clearly shown in the drawing. Rotatable in the bearings Hit] is the sleeve-like hub |6| of a relatively large face gear |52 having a splined bore |63 disposed in axial alignment with the axis of the compressor shaft |52.

Fastened to the rearward face of the air discharge member |5| is a cup-shaped support member |55 which has a bore in which the rearward end of a relatively short shaft |55 is rotatable, the forward splined end |51 of this shaft engaging in the splined portion |55; of the compressor shaft |52 so as to be rotated thereby, the shaft |55 being provided with a gear l. A plurality of larger gears, one of which is shown at il@ as rotatable on a pin 1| extending between the sides of the lower forked end of the support member |65, meshes with the gear its to be driven thereby. Rotatable within an anti-friction bearing |12, mounted in the support member |55, is one end of a hub member |73, the other end of which is secured within the hub portion i6! of the ring gear |62. The hub member |13 carries a ring |15 having internal gear teeth meshing with the teeth of the gear Vic. By this arrangement of gears, when the compressor unit is in operation, power is transmitted from the shaft |52 through the gear |68, gear gt and ring gear |15 to rotate the hub member |13 and the ring gear |62 connected thereto.

The power derived from the shaft |52 can be utilized for driving machines or equipment of various-types. As an example, the power transmission mechanism illustrated in Fig. 2 may be advantageously employed for driving an electrical alternator, such as indicated at'v |125. In this case, the shaft |18 of the alternator |11 has a splined end which engages in the splined bore of the gear hub ISI so as to be rotated thereby. It is thus seen that when the compressor shaft |52 is rotated, the alternator Ulis-operated thereby. As will be apparent, it is necessary that the alternator |11 be operated at a constant speed and this is attained by operating the compressor at a constant predetermined speed.

The power transmission described above also operates accessories for the turbo-compressor power plant, one of these being an oil pump |811 which is boltedto the bottom of the transmission housing |51. The` pump has a shaft |8| provided with a gear |82 which meshes with a similar gear |83 formed integral with the hub of the ring gear |62. It is thus seen that during operation of the air-compressor the oil pump |89 is driven thereby. 'Ihe shaft |il| is connected to operate a fuel pump |85 attached to the lower end of the oil pump |80, this connection and the pumps being of any suitable construction and therefore not disclosed in detail.

An electrical starter |86 has its casing |81 secured to the annular wall of the transmission housing |51 and has a shaft |88 provided with a gear |89 disposed within the housing and meshing with the ring gear |62. To start the turbocompressor power plant, the starter |86 is energized to cause its gear |89 to rotate the ring gear |62, hub member |13, gears |10 and |58, shaft |65 and compressor shaft |52. After the turbocompressor power unit attains the speed necessary for operation, the starter |85 is automatically or manually deenergized. fm overrunning clutch |90 (Fig. 7) is employed for the purpose of disconnecting the starter shaft |88 from the turbine, this clutch being similar to and functioning in the same manner as the clutch |29, discussed previously.

I claim as my invention:

A power plant, comprising: an air compressor unit having a double-volute compressed air discharge housing; a hot gas turbine unit having an inlet housing and a driving connection with said compressor unit; a single pair of discharge ducts for compressed air, said discharge ducts being laterally spaced from the opposite sides of the power plant and respectively connecting said volutes with said turbine inlet housing; a combustion chamber in each of said discharge ducts between said units; a bleed connection for bleeding compressed air from each of said discharge ducts prior to reaching said combustion chambers; and an air inlet connection for said compressor unit, said air inlet connection intersecting a pla-ne normal to the power plant axis which plane passes through both said combustion chambers, said air inlet connection being substantially equally angularly spaced from both said combustion chambers, and said air inlet connection being substantially spaced upwardly from a plane eX- tcnding through the upper surfaces of both of said combustion chambers, whereby air is supplied to said compressor unit without substantial heating by said combustion chambers to permit air to OTHER'REF'ERENCES The-Aviation News,x Feu-1947; pages 49-523 

